You might assume that there has always been water on Earth — that water was there from the very beginning when our planet formed. But scientists increasingly think that water on Earth may have originated elsewhere, and been carried here by comets. However, the water in the comets had to come from somewhere, and astronomers recently made a discovery which could shed light on how that water was found in the solar system.
The researchers used the Atacama Large Millimeter/submillimeter Array (ALMA), a radio telescope array in Chile, to study a planet-forming disc around the star V883 Orionis, looking for water there to see how it would be transported as the disk evolves into planets.
They were able to compare two different types of water, the one that has one oxygen atom and two hydrogen atoms that we know well, and the other, which is a heavier type of water that has one oxygen, one hydrogen, and one deuterium (a stable isotope of hydrogen) atom. These types of water form differently, so scientists can use the ratio of normal to heavy water as a fingerprint to see how old the water is and where it comes from.
This is important because the water in V883 Orionis’s disk has similar properties to the water seen in our solar system. “V883 Orionis is the missing link in this case,” said lead researcher John J. Tobin of the National Radio Astronomy Observatory, in a statement.
“The composition of the water in the disc is very similar to that of comets in our own solar system. This is confirmation of the idea that the water in planetary systems formed billions of years ago, before the sun, in interstellar space, and has been inherited by both comets and Earth, relatively unchanged.”
This evidence suggests that water was around in the region of space that would become the solar system before the planets and star even formed. “We can now trace the origins of water in our Solar System to before the formation of the sun,” said Tobin.
Next, the researchers want to use the upcoming Extremely Large Telescope to look for other planet-forming disks and see how water moves through the disks as planets form.
The research is published in the journal Nature.
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